The influence of the photoperiodic regime and red-far red light treatments of Portulaca oleracea L. plants on the germinability of their seeds

Plants of Portulaca oleracea L. were grown in a temperature controlled greenhouse. In one experiment plants received 8 hrs of daylight and during the following 16 hrs ("dark period") they either were grown in darkness or received white, red and far red light of low intensity for various times preceeding the dark period or in the middle or the end of the dark period. In other experiments the plants were grown in photoperiods of 8, 11, 13, 15, 16 hrs and in continuous light. The effect of these treatments on number of leaves until the appearance of the first flower bud and the germination of the seeds collected from these plants were studied. P. oleracea was found to be a photoperiodic facultative or quantitative short day plant. The photoperiodic treatments of the mother plants affect the germinability of their seeds, dependent on the last 8 days of seed maturation on the mother plants. The shorter the daylength the faster the germination. Red or far-red treatments of the mother plant also affect the germinability. But in no case is there dark germination even after 8 days of seed maturation under continuous red light. These results suggest that the influence of the light treatments of the mother plants on the germination of its seeds is not mediated via phytochrome but rather through some other pathway.